A1 noun Neutral #2,706 most common

直径

chokkei [tɕokːeː]

The distance from one side of a circle to the other, passing through the center point. It is a fundamental measurement used in geometry and daily life to describe the size of round objects like plates or pipes.

Examples

3 of 5
1

このピザの直径は30センチです。

The diameter of this pizza is 30 centimeters.

2

太陽の直径は、地球の約109倍です。

The diameter of the sun is approximately 109 times that of the Earth.

3

ねえ、このボールの直径ってどれくらい?

Hey, what is the diameter of this ball?

Word Family

Noun
直径
Related
半径
💡

Memory Tip

The first kanji 直 (choku) means 'straight.' Think of a 'straight' line passing directly through the middle of a circle.

Quick Quiz

円の___は、半径の2倍の長さです。

Correct!

The correct answer is: 直径

Examples

1

このピザの直径は30センチです。

everyday

The diameter of this pizza is 30 centimeters.

2

太陽の直径は、地球の約109倍です。

formal

The diameter of the sun is approximately 109 times that of the Earth.

3

ねえ、このボールの直径ってどれくらい?

informal

Hey, what is the diameter of this ball?

4

円の面積を計算するには、直径ではなく半径が必要です。

academic

To calculate the area of a circle, you need the radius, not the diameter.

5

このパイプの直径は、規格に合わせて50ミリにしてください。

business

Please ensure the diameter of this pipe is 50mm according to the standards.

Word Family

Noun
直径
Related
半径

Common Collocations

直径を測る to measure the diameter
直径5センチ 5cm in diameter
直径が大きい to have a large diameter
最大直径 maximum diameter
直径を計算する to calculate the diameter

Common Phrases

直径に等しい

equal to the diameter

内径と外径

inner diameter and outer diameter

直径の長さ

the length of the diameter

Often Confused With

直径 vs 半径

Hankei (radius) is half the distance of the diameter (chokkei).

直径 vs 円周

Enshū (circumference) is the distance around the circle, not across it.

📝

Usage Notes

While commonly used in math, it is also frequently used when buying household items like frying pans, pots, or lightbulbs.

⚠️

Common Mistakes

Learners often confuse 'chokkei' (diameter) with 'hankei' (radius). Also, avoid using 'nagasa' (length) alone when the specific dimension needed is the diameter of a circle.

💡

Memory Tip

The first kanji 直 (choku) means 'straight.' Think of a 'straight' line passing directly through the middle of a circle.

📖

Word Origin

From the kanji 直 (direct/straight) and 径 (path/diameter). It literally means the 'straight path' through a circle.

Grammar Patterns

Used as a standalone noun. Often follows the pattern [Noun] + の + 直径. Can be followed directly by measurements (e.g., 直径10cm).
🌍

Cultural Context

In Japan, many household goods are categorized by diameter using the unit 'cm' or 'mm', which is essential for home shopping.

Quick Quiz

円の___は、半径の2倍の長さです。

Correct!

The correct answer is: 直径

Related Words

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